Atomic-vacancy ordering and magnetic susceptibility of nonstoichiometric hafnium carbide

Experimental data on the magnetic susceptibility of nonstoichiometric hafnium carbide HfCy(0.6< y<1.0) are presented. Anomalies are found in the temperature dependences of the magnetic susceptibility of the carbides HfC0.71, HfC0.78, and HfC0.83 in the temperature range 870–930 K. These anomalies are due to the formation of a superstructural short-range order in their nonmetallic sublattice. It is shown that the short-range order in the carbides HfC0.71 and HfC0.78 corresponds to the ordered phase Hf3C2, while in the carbide HfC0.83 it corresponds to the ordered phase Hf6C5. It is found that the magnetic susceptibility of the carbide HfC0.78 in the temperature interval 910–980 K is zero.